AC conductivity and dielectric studies in V2O5-TeO2 and V2O5-CoO-TeO2 glasses

Single and mixed transition metal ions doped tellurite glasses were investigated for dielectric properties in the frequency range 50 Hz to 5 MHz and temperature range 300-500 K. From the total conductivity derived from the dielectric spectrum the frequency exponent, s, and dc and ac components of the conductivity were determined. The temperature dependence of dc and ac conductivities at different frequencies was analyzed using Mott's small polaron hopping model and, the high temperature activation energies have been estimated and discussed. The frequency exponent, s, was compared with theoretical models. The ac conductivity variation with frequency has been fit to Hunt's expression given for omega > omega(m) and the fit was found to be good which reveal that Hunt's model explains the measured data satisfactorily in the experimental frequency domain. (C) 2008 Elsevier B.V. All rights reserved.